Aircraft uplock mechanisms are designed to lock the landing gear in a retracted position and assist in carrying the weight of the gear during flight. Conventional uplock mechanisms consist of a spring-loaded catch that locks the gear in place and a hydraulic cylinder to release the locking mechanism to free the gear to be lowered for landing.
Current aircraft systems typically use a multitude of hydraulic subsystems as a source of mechanical energy. Typical state of the art uplocks employ one hydraulic actuator to perform the unlocking function, and often use a manually actuated cable system to perform the unlocking in the case of a hydraulic system failure. Other existing uplocks employ a secondary hydraulic actuator for the alternate release. Disadvantageously, hydraulic actuation system are complex and add unnecessary additional weight for the aircraft to carry.
There has been a trend in the aircraft industry toward electrical actuation systems. An overall reduction in aircraft weight can be observed through the use of electrical systems in preference to hydraulic systems. However, electrical actuation systems are complex to manufacture and not fully reliable.
To meet the challenge of releasing an uplock using electrical energy, two approaches have been investigated. In the first approach, an electromagnetic solenoid can be employed as the principal release actuator. Solenoids typically offer relatively low force per unit of mass, but they are simple and reliable. Solenoid systems can be employed where the weight of the landing gear can be lifted off the uplock hook prior to the solenoid being activated. In the case of a failure in which the landing gear lifting mechanism becomes inoperable, the weight of the gear on the hook would be too much for the solenoid to release. Systems employing solenoids for primary release also have a secondary release mechanism. This release mechanism can be of the manual, cable operated variety, but typically an electromechanical actuator is employed. An electromechanical actuator uses an electric motor coupled to a gearbox to provide a high force/torque actuation system. Electromechanical actuators have a high level of complexity and a number of vexing failure modes.
Accordingly, there is therefore a need for an aircraft landing gear actuation system which allows the release of the uplocks such as to obviate or mitigate at least some of the above presented disadvantages. Additionally, there is a need for an actuator which obviates or mitigates at lease some of the above presented disadvantages of actuators.